Hollow core door with internal air flow

ABSTRACT

Hollow core door apparatus for preventing the build up of pressure in a room having a register through which air flows into the room and a center panel in the door with at least a single opening through the center panel; the door has an inside door skin and an outside door skin, both of which include openings spaced apart from the center panel, and an inside panel and an outside panel disposed in the respective openings in the inside and outside door skins. The inside and outside panels are spaced apart from the center panel within the respective door skin openings, and the spacing within the door skin openings define peripheral openings at least as great as the area of the opening in the center panel and are offset from the opening in the center panel to provide for a non-linear flow of air through the door to prevent the build up of pressure in the room. Several different embodiments are illustrated. An embodiment combining a noxious gas absorbent material with the pressure build up prevention capabilities is also illustrated.

CROSS REFERENCE TO RELATED APPLICATIONS

THIS APPLICATION IS A CONTINUATION IN PART OF application Ser. No.12/927,766, FILED Nov. 23, 2010.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

NOT APPLICABLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to doors, and, more particularly, to hollow coredoors having internal openings through which air flows for preventingair pressure from building up in closed rooms.

2. Description of the Prior Art

Hollow core doors have been made for many years for inside doors. Thehollow core doors are less expensive than solid core doors, are easierto manufacture, and they are rigid and hence resist warping andtwisting. Such hollow core doors make up the largest share of insidedoors where strength and security are not required.

A hollow core door generally includes a perimeter frame of a pair ofvertically extending stiles and a pair of horizontally extending rails.The perimeter frame is covered typically with plywood panels adhesivelysecured to the perimeter frame. There are also inside frame elements,typically wood strips extending horizontally between vertical framemembers or in an “x” configuration within the perimeter frame.

With the advent of cheaper materials, such as hardboard and mediumdensity fiberboard (mdf) to replace the plywood, the construction ofdoors became less expensive using the cheaper materials than themanufacture of doors using the more expensive plywood panels or coversor skins. However, the use of hardboard and mdf also requires a binder,and the most commonly used binder is a urea formaldehyde resin orcompound. In other words, the substances out of which panels for hollowcore doors are made inherently include, under contemporary manufacturingprocesses, at least a single noxious material.

The use of urea formaldehyde contributes to what is sometimes referredto as “Sick Building Syndrome.” This syndrome is caused by the gasemissions from the formaldehyde and from other chemicals used in the newdoor products and from other products in the home that also useformaldehyde resin or binder, such as furniture, kitchen cabinets, woodflooring, counter tops, wallpaper, carpet, and even paint.

There may also be other factors contributing to the Sick BuildingSyndrome, such as poor ventilation, combustion gases, fumes fromattached garages, high auto traffic, tobacco smoke, and various volatileorganic chemicals or VOCs. However, formaldehyde compounds or productsprobably contribute most to the Sick Building Syndrome and to thediscomfort of people in the building or structure.

One solution, or partial solution, to the syndrome is to reduce the useof formaldehyde products. Another solution is to provide a product orproducts that absorbs and decomposes the formaldehyde gases and othernoxious gases or products. The present invention includes absorbentmaterial which absorbs and decomposes formaldehyde gases and othernoxious materials and removes them from within the hollow core door andfrom air passing through the hollow core of a door to help clean the airwithin the room and building in which the door is located.

Moreover, the use of several doors in a house or building, such as oneor more doors in each room, provides sufficient area on which isdisposed the absorbent material for cleaning or scrubbing the airflowing through the doors. It is noted that typically each room in ahouse has at least one door, and rooms may have more than one door whencloset doors, etc., are taken into consideration. The more doors in ahome or building, the more efficient the scrubbing or cleaning processbecomes.

It is also noted that in the case of new construction, doors are usuallyinstalled towards the end of the construction period, but prior tooccupancy. It is important to clean the air of all the noxious materialoccasioned by the construction, such as paints, adhesives, smoking, newfurniture, etc., prior to occupancy. The use of fans to change the airafter construction and prior to occupancy may remove much of the noxiousmaterials, but VOCs and adhesive gases may continue to outflow fromtheir sources for a substantial period of time after construction andafter occupancy. The present invention helps to remove those noxiousmaterials from the air on a continuing, long term basis.

Hollow core doors also have an advantage in that the hollow core isideal for including pressure equalization elements to prevent airpressure from building up within a closed room. Such air pressure buildup in a room interferes with the proper circulation of heated or cooledair in a forced air system.

Typically, there are no cost effective ways to prevent the increase inpressure in a closed room relative to a return air space. The return airspace in a house is usually a hall which has a return air duct whichconveys return air back to an air handler.

Several embodiments of hollow core doors of the present inventionovercome the problem of preventing pressure build up in a room and atthe same time provide substantial privacy relative to both light andsound. Moreover, the air scrubbing and pressure build up structures maybe combined to provide a “smart door” That performs both a scrubbingfunction and a pressure build up prevention function.

SUMMARY

The invention described and claimed herein includes an interior doorwith a core having openings through which air passes between a room anda return air area for equalizing the pressure in the room and in thereturn air area. Panels on either side of the core are spaced apart fromthe core such that flow of air through the core of the door is at leastequal to the area of an inflow vent so that there is no build up ofpressure in the room. An intake air panel and an outflow air panel aredimensioned to provide the required air flow through the door from theroom to the return air space. The dimensions of the spacing of the twopanels from the core and openings in the core provide the requisite airflow to prevent pressure build up in the room. The inner and outerpanels, together with the core and the openings therein also provideprivacy for both visual and sound between the room and the return airspace. The return air space is typically a hall or the like whichincludes an air return path to the air handler for the house orstructure.

Among the objects of the present invention are the following:

To provide a new and useful hollow core door;

To provide a new and useful hollow core door having passages through thedoor for the flow of air between the room in which the door is installedand a return air area for the flow of air through the door;

To provide a new and useful hollow core door having air flow through thedoor of a predetermined amount equal to or greater than the air flowinto the room from an air supply register to prevent the build up ofpressure within a closed room;

To provide a new and useful hollow core door having a center panelwithin the door with a plurality of openings in the center panel for theflow of air;

To provide a new and useful hollow core door having a pair of panelsspaced apart from a center panel within the door and around which airflows;

To provide a hollow core door having panels spaced apart from a centerpanel which includes openings the area of which provides a predeterminedarea for controlling the flow of air through the door;

To provide a new and useful hollow core door for preventing a build upof pressure in a room by air flowing non-linearly through the door;

To provide a new and useful hollow core door apparatus for preventing abuild up of pressure in a room having a forced air system by flowing airthrough a door to a return air space;

To provide new and useful door apparatus combining an air flow throughthe door for removing noxious materials from the air flow and forpreventing a pressure build up in a room by flowing air generallynon-linearly through the door to a return air space; and

To provide new and useful apparatus for preventing a build up ofpressure in a room having a forced air system.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic representation of a door of the present inventionin its use environment.

FIG. 2 is a perspective view of a portion of the door of FIG. 1partially broken away, taken generally from circle 2 of FIG. 1.

FIGS. 3, 4, and 5 are perspective views sequentially illustrating themanufacture of a door of the present invention.

FIG. 6 is an end view of a door of the present invention.

FIGS. 7 and 8 are perspective views of alternate embodiments of aportion of a door of the present invention illustrating cores.

FIGS. 9 and 10 are plan views of more alternate embodiments of a portionof a door or the present invention illustrating core elements.

FIG. 11 is a view in partial section of a portion of another alternateembodiment of the present invention.

FIG. 12 is a view in partial section of a portion of another alternateembodiment of the present invention.

FIG. 13 is a fragmentary view of a portion of a door comprising anotheralternate embodiment of the present invention.

FIG. 14 is a fragmentary view in partial section through anotheralternate door of the present invention.

FIG. 15 is an exploded perspective view of the door of FIG. 14.

FIG. 16 is a fragmentary view in partial section of an alternateembodiment of the apparatus of FIGS. 14 and 15.

FIG. 17 is an exploded perspective view of the apparatus of FIG. 16

FIG. 18 is an exploded perspective view of another alternate embodimentof the apparatus of the present invention.

FIG. 19 is a perspective view of the assembled apparatus of FIG. 18.

FIG. 20 is a fragmentary view in partial section of the apparatus ofFIGS. 18 and 19.

FIG. 21 is a fragmentary view, partially broken away, of a portion ofanother alternate embodiment of the present invention.

FIG. 22 is a fragmentary edge view of a portion of the apparatus of FIG.21.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a schematic representation of a view of a hollow core door 10of the present invention disposed in a room 3. The room 3 is the useenvironment of the door 10. The door 10 includes a top panel 12 (seeFIG. 2) secured to a perimeter frame

Elements of the perimeter frame and portions of internal elements areshown in FIG. 2. FIG. 2 comprises a perspective view of a portion of thedoor 10 of FIG. 1, taken generally from circle 2 of FIG. 1. A portion ofa side stile 12 is shown, along with a portion of a top rail 16, and atop cover or panel 40. The top rail 16 includes a plurality of openingsor holes 18 through which air flows vertically within the door 10. Alsoshown in FIG. 2 is a portion of an upper internal brace element 24. Theelement 24 includes a plurality of spaced apart holes or openings 26through which air may flow.

The door 10 and a method of making the door is illustrated in FIGS. 3,4, and 5. FIGS. 3, 4, and 5 are consecutive or sequential perspectiveviews illustrating the steps used to make the door 10. FIG. 5 alsoillustrates the internal bracing of the door 10. FIG. 6 is an end viewof the completed door 10. For the following discussion, reference willbe primarily directed to FIGS. 3, 4, 5, and 6.

A central portion 52 of an outer door panel or skin 50 may be roughsanded by a belt sander 2 after parallel rabbets 54 and 56 are machinedinto the panel 50. Obviously, an automatic sanding machine, not shown,may be preferable to the hand operated belt sander 2 shown in FIG. 3 ifsuch sanding is deemed desirable. The purpose of the sanding is toacquire better adhesion of the absorbent material to the panels of thedoor. Other methods may also be used, such as paint or other adhesive.

The stiles 12 and 14 extend into the rabbets 54 and 56, as best shown inFIG. 6, when the outer panels are ready to be secured to the perimeterframe and to any internal frame elements.

After the rough sanding or sealing of the panel, an absorbent, such asdiatomaceous earth, is applied to the rough sanded portion 52 of thepanel 50. In FIG. 4, the absorbent material is schematically representedby reference numeral 60 being applied from a can or cup 4 or otherdesired element to form a layer on the sanded portion 52 of the panel50.

It will also be noted that paper impregnated with an absorbent materialmay also be adhesively secured to the panel portion 52. Paper strips aresometimes adhesively secured to the inside portions of the outer panelsor skins to provide stiffness. The strips may be impregnated with anabsorbent, as noted.

The layer 60 is a special absorbent material which also may include anappropriate binder to secure the adhesion of the absorbent material tothe panel 50. A water based paint may be used if desired. A scraper ortrowel 6 is shown in FIG. 4 as smoothing the layer of absorbent material60 on the panel 50 to insure an even coating on the panel.

It will be noted that any appropriate method of applying the absorbentmaterial may be used. For example, rollering, spraying, troweling, etc.,may be desired under various circumstances, such as when automating theprocess, or when a particular type of absorbent material used, etc.

Absorbent materials, such as diatomaceous earth and other materialswhich may also contribute to the absorption and decomposition offormaldehyde and noxious material may be includes in the absorbentmaterial layer 60. A benefit of using diatomaceous earth, in addition toits absorbent capability, is the destruction of noxious insects. It iswell known that insects which eat diatomaceous earth die of dehydration.Thus, the absorbent material layer 60 provides a pest control service,in addition to the absorption and decomposition of formaldehyde gasesand tobacco smoke ingredients, and other noxious gases.

Other materials such as gypsum, sodium sulfate, manganese dioxide,aluminum oxide, titanium dioxide, potassium permanganate, tourmaline,various types of carbon or charcoal, and other materials currently beingused or being developed, may also be included or used as or in theabsorbent material layer 60.

Furthermore, the use of nano scale materials may also be used to scrubnoxious materials, such as volatile organic chemicals (VOCs), from air.Nano scale materials, such as the tourmaline referred to in thepreceding paragraph, are being developed for scrubbing noxious materialsfrom air, but at the present time the use of such technology is in itinfancy. In the future, such materials may be advantageous for use withthe structure set forth herein.

The steps illustrated in FIGS. 3 and 4 are accomplished on the innersurfaces of both panels 40 and 50. Sequentially, after both panels havereceived the absorbent or scrubber material, the panels are secured tothe perimeter frame and to the internal bracing or core. For example, inFIG. 5 the bottom panel 50 is shown secured to the stiles 12 and 14 andto the rails 16 and 20. Both rails 16 and 20 include the holes orapertures 18 and 22, respectively. Internal horizontal bracing or coreelements 24, 28, and 32 are secured to the panel 50 and to the stiles 12and 14. The elements 24, 28, and 32 each have a plurality of holes orapertures 26, 30, and 34, respectively, to allow for the flow or aircontinuing through the core of the door 10.

FIG. 6, an end view of the door 10, shows the stiles 12 and 14 and thebottom rail 20 with is apertures 22, and the panels 40 and 50. Note thatthe panels 40 and 50 have been arbitrarily been designated “top” and“bottom” for convenience. The “top” panel 40 is also designated as the“front” panel, above.

The steps illustrated in FIGS. 3 and 4 are repeated for the top panel40, and the panel 40 is then secured to the perimeter frame and to thecore elements.

FIG. 7 is a perspective view of a portion of an alternate embodiment ofthe present invention, comprising hollow core door 70. The door 70includes a pair of spaced apart stiles 72 and 74 and a pair of rails 76and 80 secured to the stiles.

The rail 76 is a top rail, and it includes a plurality of spaced apartholes 78 through which air flows. The rail 80 is a bottom rail, and itincludes a plurality of spaced apart holes 82 through which air flows.

A lower horizontal cross brace 90 is spaced apart upwardly from the rail80. The cross brace 90 includes a plurality of holes or openings 92through which air flows. The holes 82, 92, and 78 are preferably alignedwith each other to facilitate the air flow. However, the holes need notbe aligned. Air will flow through the core of the door 70 generallyregardless of the orientation or alignment of the various holes in thehorizontally extending elements.

A pair of lock blocks 84 and 86 are secured respectively to the stiles72 and 74. The pair of lock blocks 84 and 86 insure that the door 70 maybe hung for either right handed or left handed movement.

Note that lock blocks, secured to the stiles, are not shown in most ofthe figures of the drawing herein. Such lock blocks are well known andunderstood in the door industry and have been omitted for convenienceand clarity of illustration.

A pair of vertically extending brace elements 94 and 96 extend betweenthe horizontal brace 90 and the top rail 76 and are appropriatelysecured thereto. Since the vertical elements 94 and 96 do not interferewith the flow of air through the core of the door 70, no holes need bedrilled through them. A second pair of vertical elements 98 and 100extend between the brace 90 and the bottom rail 80.

A panel 102 is appropriately secured to the stiles, the rails, theinternal brace elements, and the lock blocks.

FIG. 8 is a perspective view of another alternate embodiment of aportion of a door 110 of the present invention.

The door 110 includes a pair of stiles 112 and 114 and a pair of rails116 and 120. The top rail 116 includes a plurality of spaced apart holes118 through which air flows. The bottom rail 120 includes a plurality ofspaced apart holes 122. The stiles and rails are appropriately securedtogether, as are the stiles and rails in the previously discussedembodiments.

Within the door frame of the stiles and rails is a horizontal brace 124.The brace 124 includes a plurality of holes or openings 126. A bottompanel 130 is appropriately secured to the frame elements, including thestiles, the rails, and the brace 124. An absorbent layer 132 is in turnsecured to the panel 130.

Secured to the panel 130 are spacer blocks 140. The blocks 140 aredisposed both above and below the horizontal brace 124. The blocks 140are spaced apart so as not to impede the flow of air through the core ofthe door 110. A top panel, not shown, is in turn secured to the blocksand to the frame members 112, 114, 116, 120, and 124, and to theinternal brace blocks 140. The internal blocks and the brace element 124provide internal strength for the door. Note that lock blocks are notshown for the door 110. Such blocks are, of course, required.

FIG. 9 is a partial plan view of a hollow core door 160, which isanother alternate embodiment of the present invention. The door 160includes a pair of stiles 162 and 164, and a pair of rails of which onlya bottom rail 170 is shown. The rail 170 includes a plurality of holes172 extending through the rail for the flow of air within the door 160.

The internal bracing for the door 160 includes a horizontal brace 176extending between and secured to the stiles 162 and 164. The brace 176includes a plurality of holes 178 through which the air flows.

The internal bracing also includes two pair of x members, an upper pair186 and 190, and a lower pair 196 and 200. The member 186 includes aplurality of holes 188 and the member 190 includes a plurality of holesor openings 192. The lower members 196 and 200 include holes 198 and202, respectively. Thus, air flows through the holes 172 in the rail170, through the holes 198 and 202 in the x members 196 and 200,respectively, through the holes 178 in the horizontal brace 176, throughthe holes 188 and 192 in the upper x members 186 and 190, respectively,and through holes in the upper rail, not shown.

Secured to the frame of the door 160 is a bottom panel 206. Anappropriate absorbent material, such as diatomaceous earth in anappropriate binder, is secured to the panel 206 and to a top panel, notshown. As the air flows through the hollow core of the door 160, throughthe various holes, past the absorbent material on both the bottom panel206 and the top panel, formaldehyde compounds and other noxious gases ormaterials are filtered out.

FIG. 10 is a plan view, partially broken away, of another alternateembodiment of a frame and core structure of a door 210. The door 210includes a pair of stiles 212 and 214 and a pair of rails, of which onlya lower rail 220 is shown. The rail 220 includes a plurality of holes oropenings 222 extending through the rail for the flow of air. The stiles212 and 214 and the rails are appropriately secured together and definethe perimeter frame for the door 210.

A horizontal brace 224 extends between and is secured to the stiles 212and 214. A plurality of holes 226 extend through the brace 224 for theflow of air. Above the brace 224 are a pair of vertically extendingbraces 228 and 230. The braces 228 and 230 extend between and aresecured to the upper rail, not shown, and the brace 224. A similar pairof vertically extending braces 232 and 234 extend between and aresecured to the bottom rail 220 and the horizontal brace 224.

A bottom panel 238 is secured to the various members, including theperimeter frame 212, 214, 220 and the upper rail, not shown, and to theinternal brace or core elements, including the horizontal brace 224 andthe vertical elements 228, 230, 232, and 234. The panel includes anappropriate absorbent material secured thereto. An upper panel, notshown, completes the door 210, along with appropriate lock blocks, alsonot shown.

FIG. 11 is a view in partial section of a portion of a door 250 whichincludes a full length inner panel 270 with absorbent coatings 272 an274 on both sides. The panel 270 comprises a single core element. Thedoor 250 includes a stile 252 with a dado groove 254 which receives thepanel 270. The door 250 also includes two outer panels 256 and 260. Thepanels 256 and 260 includes rabbets 258 and 262 into which the stile 252extends.

A pair of spacers 276 help to center the panel 270 between the outerdoor panels 256 and 260. The spacers 276 are aligned with each other forproper support, and additional pairs (not shown) are spaced apart asappropriate between stiles.

It will be noted that the inside of the panels 256 and 260 may also becoated, as discussed above for the doors 10, 70, 110, 160, and 210.Using four such surfaces for the absorbent material provides nearlyseventy five square feet of absorption area.

The panels 256 and 260 may be mdf or other appropriate material, asdesired.

FIG. 12 is a view in partial section of a portion of a door 280 whichincludes two outer panels 290 and 294 and two absorbent inner panels 300and 304 as part of the core elements. The door 280 includes a stile 282which extends into rabbets 292 and 296 in the outer panels 290 and 294,respectively, and a relatively large dado groove 284 into which extendthe panels 300 and 304. A plurality of spacers 310 hold the panels 300and 304 apart within the door 280. The spacers 310 are spaced apartbetween stiles as needed for supporting and spacing the panels 300 and304. Note that the first spacer 310 extends into the dado groove 284between the outer ends of the panels 300 and 304.

The panel 300 includes a recess 302 and the panel 304 includes a recess306. The recesses 302 and 306 increase the surface of the panels 300 and304, respectively for absorption purposes.

The panels 300 and 304 may be gypsum, without the paper or cardboardcovers which wall board (gypsum board) has, and that have had materialsdiscussed above added to them for scrubbing. The panels 300 and 304 mayalso be a pair of panels such as the panel 270 of FIG. 11. However,gypsum has qualities which lend credence to its use as singular panels.

A special quality of gypsum, in addition to is general absorbencycapabilities, is that it absorbs moisture from the air when there ishigh humidity and releases the moisture when the humidity is low. Theuse of gypsum accordingly decreases mildew and mold growth in astructure, in addition to increasing the comfort level in the structure.

Another property or quality of gypsum is that it helps to absorb sound.Thus, the use of a door 280 with a pair of gypsum panels reduces thesound level in a structure in which such a door/doors is/are installed.

Another property or quality of gypsum is its fire retardant ability. Thedoors with the gypsum panels thus provide fire protection within astructure not otherwise contemplated by prior art hollow core doors.

As an alternative to two gypsum panels within a door, a single gypsumpanel, such as the panel 300, may be paired with a panel such as thecoated panel 270 of the door 250. Such door combination provides amixture of the capabilities or qualities or advantages of the variousabsorbents.

Note that the panels 270, 300, and 304 comprise core bracing elements inaddition to their absorption functions. The spacer elements used inconjunction with the inner panels also contribute to core bracing fortheir doors.

Referring again primarily to FIGS. 2, 5, and 6, the top and bottom railsshow openings or holes 18 and 22, respectively. If only formaldehydegases or other noxious materials within an mdf door or the like wereconsidered, such openings or holes in the rails may be eliminated. Withabsorbent material, such as diatomaceous earth, within the core, theformaldehyde products would be absorbed and decomposed. Holes oropenings may still be located within internal bracing elements, ifdesired. However, the internal bracing elements may also be withoutholes if the internal absorbent is located similarly to that shown inFIG. 5. Obviously, the location and quantity of the absorbent materialwill be as appropriate for a particular door.

Moreover, if absorbent and decomposing materials, such as diatomaceousearth and gypsum, etc., are incorporated into the construction of themdf or similar material, then such materials need not be added to theinside of the panels themselves. Rather, the addition of the scrubbingmaterials to the mdf or similar material in the making of the panelssimplifies the scrubbing situation.

However, the inclusion of the scrubbing materials into the panels maynot be sufficient if the filtering or scrubbing of an air flow through ahollow core door is desired. In such case, the addition of scrubbingmaterial or materials within the hollow core as described above isdesirable.

While diatomaceous earth and other materials have been mentioned ordiscussed above as appropriate absorbent materials for formaldehyde andother noxious material in the gases in the air flowing through thehollow core of a door, there are other appropriate absorbent ordecomposing materials, such as activated carbon or charcoal, withappropriate additives, and other materials which also may be used forabsorbing and decomposing formaldehyde and other noxious gases in theair flowing through the internal core of the hollow doors discussedabove. And in the future there will undoubtedly be other materials toperform the same basic scrubbing functions.

Moreover, one panel, a top panel for example, may use one type ofabsorbent or decomposing material, while the other panel, a bottompanel, may use another type of absorbent or decomposing material. Orseveral types of such materials may be used on each panel. The use of aparticular one or more materials may depend on the particular situationsor locations for or at which the doors are made or are installed. Theremoval of noxious materials from air flowing through the hollow core ofa door may include different types of absorbent or decomposing or otherproducts. Noxious material may take the form of compounds, odors,moisture, etc., and combinations of such things.

The removal of such noxious material may require absorption,decomposition, or other technique—chemical, mechanical, etc. The flow ofair in a structure and through the hollow core of a door carries thenoxious material, and the removal of the noxious material may require acombination of products, techniques, etc.

Another technique may also be used to remove noxious materials, and thattechnique is to use a photocatalyst, such as titanium dioxide. Aphotocatalyst, such as titanium dioxide reacts to light, such as ultraviolet light, and breaks down into hydroxyl radicals and super oxideanions. The products of the photocatalytic process oxidize noxiousmaterials, such volatile organic compounds, formaldehyde, and othermaterials as referred to above, etc.

Ambient light, direct sunlight, or an artificial light source, may beused to provide the necessary light to catalyze the photocatalyticmaterial. The photocatalytic process will continue as long as there islight to cause the photocatalytic to take place.

Accordingly, referring to FIG. 1, the exterior of the door, or the doorfacings, may be coated with titanium dioxide or other photocatalyticcompound. In the presence of light, sunlight or ambient light, thephotocatalytic process takes place, removing noxious products.

Referring to FIG. 13, if such photocatalytic coating is placed on theinside of hollow core doors, an artificial light source must be providedin order to cause the photocatalytic process to take place.

FIG. 13 is a schematic representation of a portion of a hollow core door330 having an artificial light source and associated elements. The door330 includes a stile 332 and a top rail 336. Extending through the rail336 are shown two holes or apertures 338 through which air flows fromthe interior of the door 330. The door 330 also includes a top panel 346and a rear or back panel 348.

Extending downwardly from the rail 336 is a battery and lamp compartment360. The compartment 360 includes a top cover 362. Extending outwardlyfrom the compartment 360 is a lamp 364. Replacement of the battery orbatteries for providing current for the lamp 364 is by way of the cover362. The cover 362 is flush with, or slightly recessed below, the top ofthe rail 336.

Within the door 330, either on the inside of the panels 346 and 348 isphotocatalytic material, and the lamp 364 provides the appropriatelight, such as uv light, to initiate the photocatalytic process. Ifdesired, there may be additional light sources secured within the hollowcore, in compartments such as 360, and attached to the rails or stiles,as appropriate or as desired.

If the airflow through the door 330 by normal convective processes isdeemed insufficient, a relatively small fan may be incorporated into thedoor. Referring again to FIG. 13, a fan 366 may be substituted for thelamp 364 for moving the air. In such case, the fan 366 may be disposedat the top of the door 330, as shown, or it may be disposed at thebottom of the door to achieve the air flow.

It will be noted that the term “gases” is to be broadly construed andincludes water vapor or moisture in the air, as well as odoriferousgases, and other noxious materials or compounds in the air within astructure. The term “gases” is thus not limited to formaldehyde orsimilar gases.

It will also be noted that doors made out of mdf products have beendiscussed and illustrated because of the use of formaldehyde resin orbinders commonly used in the manufacture of mdf products, andformaldehyde is probably the leading noxious material. However, a hollowcore door made of steel, fiberglass, wood, or other products, may alsobe used with absorbent, decomposing, etc., material within the hollowcore for removing or neutralizing noxious material or products or gasesfrom air flowing through the hollow core. The scrubbing of noxiousmaterial from air flow accordingly may require a combination ofmaterials secured within the hollow core of a door regardless of whatthe door is made of.

The terms “scrubber,” “scrubbers,” and “scrubbing,” all refergenerically to the various kinds or types of material which may be usedto remove noxious materials from the internal air flow within the coreof a door.

It will further be noted that as used herein, and in the followingclaims, the terms “material” and “materials” are virtuallyinterchangeable, with “material” being considered both, or either,singular or plural.

The terms “absorb” and “absorbent,” etc., have been used hereinregarding appropriate materials for carrying out the purposes of thepresent invention. It will be understood that “adsorb” and “adsorbent”materials may also be used to carry out the purposes of the presentinvention. Essentially, for purposes herein, the terms areinterchangeable. Moreover, it will be understood that a combination ofabsorbent and adsorbent materials may be used if desired in the cleaningor filtering of the air flow through the hollow core doors of thepresent invention.

It will be still further noted that openings may be provided in the topand bottom structural elements of a door, and in structural or otherelements within the door without regard to the material out of which thedoor is made. The terms “rails” and “stiles” refer broadly andrespectively to the top and bottom horizontal and to side verticalelements of a door perimeter frame without regard to the material out ofwhich the door is made.

Moreover, the size of the openings or holes in the rails and in theinternal core elements may vary from relatively small to rather large,depending on the desired air flow and on the absorption material withinthe core of the door.

Finally, it will be understood that airflow through a door may vary,depending on the time of day, the relative humidity, the size of theopenings in the rails and in other interior door elements, and otherfactors. For example, morning air it typically more humid, and the morehumid air flowing through a door core may be more readily absorbed intothe filtering materials than drier air. As the relative humiditydecreases during the day, the drier air minus the contaminants ornoxious materials is desorbed from the filtering material and flows outof the door. Contaminants, or noxious material, in the airflow throughthe door may still be removed from the airflow regardless of therelative humidity of the air. Furthermore, humidity itself may beabsorbed by various materials.

The changes in the humidity during the day perhaps allow the removalprocess to be more efficient. However, air flowing through the door willbe cleansed by the scrubbing material disposed within the core of thedoor by normal convection regardless of the humidity. The flowing air iscleansed of contaminants and noxious material from both the room and thedoor core internal elements, as stated above.

In addition to the removal of noxious material from an air flow throughhollow core door, a hollow core door may be used to prevent the build upof air pressure in a closed room which has a forced air system.Embodiments of such hollow core door apparatus are illustrated indrawing FIGS. 14-22 and are discussed below.

FIG. 14 is a schematic view in partial section of a portion of a door410 illustrating the concept of the present invention in an embodimentfor preventing the build up of air pressure from a flow of air 404flowing from a register 402 in a closed room 404.

FIG. 15 is an exploded perspective view of a portion of the apparatus ofFIG. 14. For the following discussion, reference may be made to bothFIGS. 14 and 15.

The register 402 provides a flow of air 404 into the closed room 400.The air flow into the room 400 is measured in cubic feet per minute(CFM). To prevent a build up of pressure in the room 400, the flow ofair through the door 410 to a return air space 434 outside the room 400should be proportional to the CFM flow of the inflow air 404. This willbe discussed in more detail below on conjunction with the structure ofthe door 410.

It will be noted that in the following paragraphs the terms “inside” and“outside” refer to the room 400. The “inside” thus refers to the insideof the room 400 and the “outside” refers to the outside of the room, orthe side of the door 410 which faces outwardly of the room and is incontact with the return air space 434.

The door 410 includes an inside door panel or skin 412, comparable tothe panel 50 as may be best understood from FIGS. 3-6. The panel 412 isappropriately secured to a top rail 411 and to a horizontal bracingelement 413. The top rail 411 is comparable to the top rail 16 of FIG.5, and the element 413 is broadly comparable to the bracing element 28of FIG. 5. A single stile 415 is shown in FIG. 14. The construction ofthe door 410 is typical of hollow core doors other than the air flowrefinements of the air flow elements. Extending through the inside doorskin 412 is an opening 414. The opening 414 may be rectangular, orcircular, etc. In the opening 414 is an inner panel 440. Theconfiguration of the panel 440 is generally the same as that of theopening 414. The air flow 404 from the register 402 flows through theopening 414 and about the inner panel 440 and into an intake air space416.

The door 410 also includes an outside door panel or skin 430, comparableto the panel 40, as may best be understood from FIGS. 2 and 6. The doorpanel or skin (generally “skin” or “skins” hereafter) 430 includes anopening 432 which is generally parallel to the opening 414 and issubstantially the same size as the opening 414. Disposed in the opening432 is an outer panel 540. The outer panel 450 is generally parallel tothe inner panel 440 and is substantially the same size.

Between the door skins 412 and 430 is a center panel 420. The centerpanel 420 includes a plurality of openings 422. Adjacent to the openings422 on the opposite side of the center panel 420 and between the centerpanel 420 and the outer panel 440 is an outflow space 424. The outflowspace 424 is generally parallel to the intake space 416 and issubstantially the same size.

The inner panel 440 includes an outer periphery or rim 442, and theouter panel 540 includes an outer periphery or rim 452. Between thepanel 440 and the center panel 420 is a plurality of spacers 444.Between the outer panel 450 and the center panel 420 is a plurality ofspacers 454. The spacers 444 and 454 secure the panels 440 and 450,respectively, to opposite sides of the center panel 420, andappropriately space the center panel 420 from the inner and outer panelsto define the size of the intake space 416 and the size of the outflowspace 424. The spaces 416 and 424 have the same area.

It will be noted that the spacers 444 and 454 are shown in FIG. 14 abeing rectangular or circular in configuration, and in FIG. 15 as beingtruncated pyramidal in configuration. The configuration of the spacersis immaterial; they may be of any desired or convenient configuration.

It will be noted that there are two peripheral spaces shown in FIG. 14.There is a first or inside peripheral space between the opening 414 andthe rim or outer periphery 442 of the inner panel 440, and through whichthe air flow 404 flows into the space 416. There is a second, or outerperipheral space between the opening 432 and the rim or outer periphery452 of the outer panel 450 through which the air flow 406 flows orpasses to the return air space 434.

There is a smooth flow of air 404 from the register 402 through theperipheral space about the rim 442 of the the inner panel 440 within theopening 414 into the intake space 416. The air then flows through theopening 422 in the center wall 420 to the outflow space 424 andoutwardly through the peripheral space about the rim 452 of the insidepanel 450 in the opening 452, and becomes an air outflow 406 to thereturn air space 434 outside the room 400, thus preventing the build upof air pressure in the room 400.

The peripheral spaces of the inside panel 440 and the outside panel 450and the size or area of the openings 422 are appropriately dimensionedto provide at least the same or greater area than the peripheral spaces.The air flow 404 thus has no constraints to flowing non-linearly throughthe door 410 and outwardly from the room 400 into an air return space434 outside the room 400.

Thus there is no build up of pressure within the room 400. That is, theair flow out of the room 400 through the door 410 is proportional to theCFM of the flow of air through the register 402 into the room 400. Thedoor 410 thus prevents the build up of pressure in the room 400.

The areas through which the air flows must provide an area proportionalto the CFM of the inflow of air through the register 402. There is arelationship between the CFM of the inflow 404 and the square inches ofthe areas through which the air flows. For example, for a 90 CFM inflow404, there should be an area of about 90 square inches through which theair flows through the peripheral space between the opening 416 and therim 442 into the space 416, and there should be at least the same 90square inches in the openings 422 for the flow of air from the space 416into the space 424. There also should be the same 90 square inches forthe air flow 406 through the peripheral space between the opening 432and the rim 542.

The distances between the outer periphery or rim 442 and the opening414, and between the outer periphery or rim 452 and the opening 432, aresubstantially the same. Those distances, and the length of the spacers444 and 454, are dimensioned so as to provide the same CFM through thedoor 410 as the CFM through the register 402 of the air flow 404. Thatis, the spacing between the rim 452 and the opening 432 defines aperipheral space to provide the desired area for the desired air flow,and is thus equal to the peripheral space between the opening 414 andthe rim 442 of the panel 440.

The square inches discussed above are the minimum areas for the CFM ofthe air flow through the register 402 into the room 400 and through thedoor 410 for the out flow 406 into the receiving space 434 to preventany increase on the air pressure in the room 400. However, the squareinches may be larger if the door permits. On the other hand, dependingprimarily on the thickness of the door, providing the necessary squareinches for the air travel through the door may require additionalelements, such as slanted panels into the air spaces 416 and 424. Thiswill be discussed below.

In terms of pressure, professional standards generally consider that thepressure in a closed room should be less than 3 pascals, or about 0.012inches of a water column. The present invention meets that criterion.

In FIG. 14, the panel 440 is shown disposed in the opening 414, and thepanel 450 is shown disposed in the opening 432. However, it will beunderstood that the panels 440 and 450 will be spaced apart from theirrespective skins 412 and 430 in or adjacent to the openings 414 and 432,respectively, to provide the necessary peripheral spacing relative tothe intake spaces 416 and 424, respectively, to provide the desired airflow.

For example, for a relatively strong air flow, in terms of CFM, and arelatively narrow door, the spacing of the panels may be outwardly fromthe door skins to provide the required peripheral spacing, or in arelatively weak air flow, and a relatively thick door, the panels may bedisposed inwardly from the door skins. Thus, the term “adjacent” may beused to define the relationship between the door skins and theiropenings and the locations of the panels relative to the openings in thedoor skins. The term “adjacent” accordingly denotes the positioning of apanel relative to the openings in the skins in, inside, or outside, theopenings.

In FIG. 15, a plurality of openings 414 are shown in the center panel420. The total area of the openings 414 is equal to or greater than thearea in square inches as discussed above.

If desired, the apparatus of FIGS. 14 and 15 to prevent pressure buildup may be provided as a framed apparatus 460, shown in FIGS. 16 and 17.As may be understood from FIG. 14, the center panel 420 is shown securedto both the inside skin 412 and the outside skin 430 at the top rail 411and the horizontal brace 413 and adjacent to the peripheral openings 414and 432 of the respective skins. Thus the top rail 411 and horizontalbrace 413 and the skins 412 and 430 and the center panel 420 form aframe. The apparatus 460 utilizes a separate frame which may be securedto inside and outside skins. The framed apparatus 460 is simply insertedinto the openings 414 and 432 and eliminates the center panel 420.

FIG. 16 is a view in partial section of a portion of the framedapparatus 460. FIG. 17 is an exploded perspective view of the framedapparatus 460. For the following discussion, reference may be made toboth FIGS. 16 and 17.

The framed apparatus 460 includes a frame 461 which includes a top framemember 462, a side frame member 464, a bottom frame member 466, and aside member 467. The frame 461 includes an inner periphery 468. Threepanels it inside the frame 461. The three panels include an inner panel470, a center panel 480, and an outer panel 490. The center panel 480 isappropriately secured to the inner periphery 468 of the frame 461.

The center panel 480 includes an opening 482 and the opening 482includes opposite side portions which cooperate with spacers 484. Aplurality of spacers 484 are secured to the panel 480 and are disposedacross the opening 482 to appropriately space the inner panel 470 andthe outer panel 490 from the center panel 480. Each spacer 484 includesslots which receive adjacent portions of the panel 480 at the opening482. The width of the spacers 484 determine the spacing of the panels470 and 490 from the center panel 480. Each spacer includes bifurcatedslots 485 which have two arms 486 and 488 and which define the slots.The opposite side portions of the opening 482 of the center panel 480are disposed in the slots and against the arms 486 and 488 of thespacers 484, as best shown in FIG. 17.

The inner panel 470 includes an outer periphery 472, and the outer panel490 includes an outer periphery 492. The space between the innerperiphery 468 of the frame 461 and the outer periphery 472 defines theintake area for the flow of air. The intake area is at least as great asor greater than the square inch requirement for the CFM air flow into aclosed room, such as the room 400 of FIG. 14, as discussed above.

The space between the inner periphery 468 of the frame 460 and the outerperiphery 492 of the outer pane 490 defines the outflow area of the flowof air through the apparatus 460. The outflow area is at least as greatas or greater than the square inch intake area, as discussed above.

The panels 470 and 490 are appropriately secured to the spacers 484. Thecenter panel 480 is secured to the center of the frame at the inner rim468. The inner panel 470 and the outer panel 490 are appropriatelydimensioned so as to provide a peripheral space between the inner rim468 and the outer peripheries 472 and 492, respectively, of the panels470 and 490 for the required intake and outflow of air, as discussedabove.

As best shown in FIG. 16, intake interior space 502 is defined by theinner panel 470 and the center panel 480. An outflow interior space 504is defined between the center panel 480 and the outer panel 490. Thepath of the inflow of air through in the peripheral space between theinner panel 470 and the inner periphery 468 of the frame 461 and intothe intake air space 502. The air then flows into the outflow air space504 through the opening 482 in the center panel 480 past the spacers484. The outflow air then flows from the space 504 and outwardly fromthe apparatus 460 through the peripheral space between the outerperiphery 492 of the outer panel 490 and the inner periphery 468 of theframe 461 to a return air space, such as the space 434 of FIG. 14.

The framed embodiment 460 may be inserted into an opening cut into anexisting door, such as in the door 410 of FIG. 14, or in a wall, atransom, etc., as desired and as appropriate.

The panels 440 and 450, and the panels 470 and 490, are smaller than theopenings into which they are respectively inserted. The difference inthe relative sizes determines the size of the peripheral area throughwhich the incoming air and the outgoing air flows. As clearly stated,the peripheral areas are as large or larger than the proportional squareinch area as discussed above.

It will be noted that there is no direct movement of the air through thedoor 410 or through the frame 460. Rather, the air takes a circuitous,or non-linear, route from the room through the door and the frame to therespective return air spaces, such as the space 434. It follows thatsound and light also have no direct path through the door.

Accordingly, privacy is maintained with respect to light and sound whena door is closed. The degree of privacy, with respect to sound is, ofcourse, dependent on the loudness of the originating sound or within areturn air space. However, ordinary sounds generally will not passeasily through the door 410 or through the frame 460, thus maintainingthe privacy within a room.

For narrow doors, a modified hollow core door apparatus may be used toprevent the build up of pressure in a closed room. Apparatus for use ina modified hollow core door with non-linear elements for preventing thebuildup of air pressure in a closed room is shown in FIGS. 18, 19, and20.

FIG. 18 is an exploded perspective view of apparatus 520 for use in arelatively thin inside door. FIG. 19 is a perspective view of theassembled apparatus 520. FIG. 20 is a view in partial section of theassembled apparatus 520. For the following discussion, reference will bemade to all of the FIGS. 18, 19, and 20.

Six elements are shown for the apparatus 520, including an inside outerframe 530, an inside center frame 550, an inside center panel 570, anoutside outer frame 580, an outside center frame 590, and an outsidecenter panel 610. All of the six elements have flat backs for assemblingthe apparatus together back to back, as shown in FIG. 20.

The inside outer frame 530 includes an inner peripheral concave quartergroove 532, and the groove terminates in a tip 534. The frame 530 alsoincludes a flat back 536.

Disposed within the inside outer frame 530 is the inside center frame550. The frame 550 includes an outer peripheral concave quarter groove552. The groove 552 terminates in a tip 534. The frame 550 also includesan inner peripheral concave quarter groove 556. The groove 556terminates in a tip 580. The frame 550 includes a flat back 560.

Disposed within the inside outer frame 550 is an inside center panel570. The panel 570 includes an outer peripheral concave quarter groove572. The groove 572 terminates in a tip 574. The panel 570 also includesa flat back 576.

The three inside elements 530, 550, and 570 have three mirror images inoutside elements 580, 590, and 610, respectively.

The outside element 580 is an outer frame element. The frame element 580includes an inner peripheral concave quarter groove 582. The groove 582terminates in a tip 584. The outer frame 580 has a flat back 586.

The outside element 590 is an outside center frame. The frame 590includes an outer peripheral concave quarter groove 592. The groove 592terminates in a tip 594.

The frame 590 also includes an inner peripheral concave quarter groove596. The groove 596 terminates in a tip 598. The frame 590 also includesa flat back 600.

The outside element 610 comprises a center panel. The panel 610 includesan outer peripheral concave quarter groove 612. The groove terminates ina tip 614. Finally, the panel 610 also includes a flat back 616.

Referring now to FIG. 20, the six elements are shown secured together ina back to back relationship or orientation to provide three elements.The three elements are generally concentrically disposed. It will benoted that the respective adjacent quarter concave grooves definerelatively widened concave generally U shaped half grooves into whichthe back to back tips extend so as to provide non-linear paths for theair flow from the inside of a room and through the door in which theapparatus 520 is installed to the return air space outside the room.

The depth to which the tips extend into their U shaped groovesdetermines the extent of the non-linearity of the air flow. The fartherinto the grooves that the tips extend provides the greatest degree ofnon-linearity for the air flow, and the greater the degree of privacywith respect to both light and sound penetration through the door.

Appropriate fastening means, not shown, such as pins, are used to securethe elements to each other and to door in which they are installed.

It will be noted that the tip and concave groove combinations may bereversed from that discussed and illustrated, if desired. For example, atip may extend outwardly from a groove on the center frame and the tipmay extend into a concave groove in the outer frame. The arrangement ofthe tips and grooves is immaterial.

Moreover, the manufacturing process discussed and illustrated may varyfrom that illustrated and discussed. For example, rather than use thesix elements, only three elements may be used, with each of the threeelements relatively thick to allow the groove and tip structure for thenon-linear flow of air through a door. And depending on the size of aroom and the air flow, perhaps only two frames, or a single frame and acenter panel, may be required to provide the desired non-linear airflowthrough a door. Or, for a larger room, three or more frames may berequired.

It will be noted that the privacy advantages of the embodiments of FIGS.14-20 are diminished in the apparatus 520. The extent of thediminishment may depend on the depth of the quarter grooves and theextent to which the tips extend into the grooves, as discussed above.

However, an advantage of the embodiment of the apparatus 520 is that itmay be configured in many designs. While a generally rectangularconfiguration is illustrated in FIGS. 18-20, it will be readily apparentthat many irregular and curved configurations may be employed foresthetic purposes.

In addition to the depth to which a tip is extended into a groove, theconfiguration of the groove with respect to a smooth air flow isimportant. The aerodynamics of the groove for the smoothest air flow isdesired. The smoother the air flow, the greater the efficiency of theair flow through a door, while still keeping the air flow non-linear, asdiscussed above.

While rounded concave elements have been shown and referred generally as“quarter concave grooves” and which are shown smoothly rounded for airflow purposes, straight, it will be understood that otherconfigurations, such relatively straight, v-shaped grooves, may also beused, if desired. The general concept remains the same—it is theaerodynamic configuration of the grooves and the depth to which a tip isinserted into a groove that determines the air flow efficiency through adoor.

It will be noted that the apparatus shown in FIGS. 14-20 may be insertedin both the upper and lower portions of a door, as required to providethe square inches necessary for the proper flow of air through the door.The apparatus of FIGS. 14-20 may also be inserted through walls, intransoms, etc., as desired to prevent the build up of pressure in aclosed room.

FIG. 21 is a fragmentary view, partially broken away, of a door 620which combines the air scrubbing capabilities of the embodiments ofFIGS. 1-13 with the air pressure build up prevention by non-linear airflow capabilities of FIGS. 14-20. FIG. 22 is a fragmentary edge view ofa portion of the door apparatus of FIG. 21.

The door 620 includes a stile 622 and a rail 626. The door 620 is shownwith an outer skin 628. A portion of the outer skin 628 is broken awayto show details of the stile 622.

The stile 622 is split to provide an air passage into the hollow coreinterior of the door 620. As may be understood best from FIG. 22, thestile 622 is split and the two portions are spaced apart by a pluralityof dowels 632. includes a passageway 624 vertically through the stile. Apassageway 624 between the two portions of the stile allows air to flowlaterally through the stile into the hollow core portions of the door.Scrubbing elements for removing noxious material, as discussed above forthe embodiments of FIGS. 1-13, remove the noxious material from the airflow.

Similarly, the rail 626 is also split and uses dowels 632 to space apartthe two portions of the rail. With split stiles and rails about theperimeter of the door, including reinforcing rails between the top andbottom rails, and holes through the bottom rail, as shown and discussedabove in conjunction with the embodiments of FIGS. 1-13, and with thescrubbing material also discussed therewith, air flow through the door620 performs air scrubbing functions, as well as preventing the build upof air pressure in a closed room when appropriate elements, such as theapparatus 410, are installed in the door.

The pressure of the flow of air into a room, such as the flow 404 of theroom 400 of FIG. 14, will provide an air flow through the door 620 to areturn air space and also through the stiles and rails for a scrubbingaction. Air will thus flow through the door to prevent the build up ofpressure and through the stiles and rails to the interior hollow corefor the air flow to be scrubbed of noxious materials.

The privacy limitations of the apparatus of FIG. 20 may limit the use ofthat embodiment in applications other than in a narrow door. On theother hand, the relatively broad esthetic design advantages of theapparatus 520 may also make that apparatus advantageous in a generallyfull length configuration for a door.

While the principles of the invention have been made clear inillustrative embodiments, there will be immediately obvious to thoseskilled in the art many modifications of structure, arrangement,proportions, the elements, materials, and components used in thepractice of the invention, and otherwise, which are particularly adaptedto specific environments and operative requirements without departingfrom those principles. The appended claims are intended to cover andembrace any and all such modifications, within the limits only of thetrue spirit and scope of the invention.

The invention claimed is:
 1. A hollow core door apparatus for preventingpressure build up in a room having a register through which air flowsinto the room comprising in combination: an inside door skin; an openingin the inside door skin having an inner periphery; a first paneldisposed adjacent to the opening in the inside door skin having an outerperiphery; a space between the inner periphery of the opening in theinside door skin and and the outer periphery of the first panelproviding a first area through which the air flows; an outside doorskin; an opening in the outside door skin having an inner periphery; asecond panel disposed adjacent to the opening in the outside door skinand having an inner periphery; a space between the inner periphery ofthe opening in the outside door skin and the outer periphery of thesecond panel providing a second area through which the air flows; acenter panel disposed between the inside door skin and the outside doorskin; and at least a single opening in the center panel comprising atotal area of which opening is at least as great as the first area andas the second area whereby the air flows non-linearly from the registerthrough the first area and through the opening in the center panel andthrough the second area to a return air space outside the room toprevent the build up of pressure in the room.
 2. The hollow core doorapparatus of claim 1 in which the center panel includes a plurality ofopenings, each of which has an area, and the total area of whichopenings is at least as great as the first area and as the second area.3. The hollow core door apparatus of claim 1 which includes a pluralityof spacers to secure the center panel to the first panel and to securethe second panel to the center panel.
 4. The hollow core door apparatusof claim 1 in which the total area of the opening in the center panel isoffset from the first area and from the second area whereby the flow ofair through the door is non-linear.
 5. The hollow core door apparatus ofclaim 1 in which the center panel is secured to the inside door skin andto the outside door skin.
 6. The hollow core door apparatus of claim 1in which the center panel includes a single opening and a plurality ofspacers secured to the center panel and the spacers are disposed acrossthe single opening and the plurality of spacers are secured to the firstand second panels.
 7. The hollow core door apparatus of claim 1 whichfurther includes a pair of spaced apart stiles; a pair of spaced apartrails secured to the pair of spaced apart stiles; a passageway extendingthrough at least one stile of the pair of stiles for providing a flow ofair through the one stile of the pair of stiles and into the hollow coreof the door; a passageway extending through at least one of the rails ofthe pair of rails for providing a flow of air through the one of therails and into the hollow core of the door; and means for scrubbingnoxious material from the flow of air through the one stile of the pairof stiles and through the one of the rails of the pair of rails into thehollow core of the door and through the first and second areas.
 8. Thehollow door apparatus of claim 7 which further includes a passageway inthe other stile of the pair of stiles for providing a flow of airthrough both stiles; and a passageway in the other rail of the pair ofrails for providing a flow of air through both rails of the pair ofrails.